Taxonomic Study Of The Family Parasitidae In China

Parasitidae(Acari: Mesostigmata: Parasitoidea)is one of the most diverse taxa in Gamasina with a world-wide distribution.Up to now,more than 500 species belonging to 46 genera in Parasitidae have been known worldwide,while only about 140 species in 14 genera have been reported in China,accounting for about 28% of the world total.It is an important decomposer group in soil and has important economic and ecological value.Currently,there have been many problems in the taxonomic study of Parasitidae in China,such as the questionable taxonomic value of the characteristics used at present,the incomplete description of some species,and the lack of in-depth investigation on the phylogenetic relationship of species.In response to these problems and deficiencies,a comprehensive and systematic morphological taxonomic study was conducted on the fauna of Parasitidae in China.Major results are followed:1.Comparative morphology and evaluation on characteristics with taxonomic implicationComparative morphology analyzed and evaluated variation types and stability of various characteristics in Parasitidae.Relatively stable characteristics within species: In female,the relatively invariant characteristics or traits within a lower taxon,species,are as follows: shape of al on femur-palp and al1 and al2 on genu-palp,dorsal seta of fixed digit on chelicera,setae z5,j5,j6,st1,pa,po,av1 or av1 and av2 on femur ?,av1,pv1,al1 and pl1 on tarsus ?–IV,and genital shield;the position of v1 and v2 on trochanter-palp,the length of corniculi;the number of dorsal shields;genital shield and ventrianal shield fused or separated;and the situation of the peritrematal shield posteriorly;claw presence or absence.In male,the relatively stable characteristics or traits within species are as below:shape of al on femur-palp and al1 and al2 on genu-palp,dorsal seta of fixed digit on chelicera,setae z5,j5,j6,pa,po,av1 and av2 on femur ?,av1 genu ?,av1 tibia ?,av1,pv1,al1 and pl1 on tarsus ?–IV,the length of corniculi and claw presence or absence.In deutoymph,the relatively stable characteristics or traits within species are recognised as length and shape of Z3,length of corniculi,shapes of setae on leg ? and sternal shield,number of opisthogastric setae.Relatively unstable characteristics within species: These characteristics may be variable among individuals within a lower taxon,species,but there are great differences in traits among different species yet.Therefore,these characteristics can still be used for identifying close species.In female,these characters and traits are known as shape v1 and v2 on palp trochanter,form of gnathotectum,dorsal shield,presternal platelets,endogynium;number and shape of opisthogastric setae;number,shape and position of idiosoma setae;the shape and length of h1–h3 and pcx;presternal platelets present or absent,sclerotic degree of sternal shield and the position of sternal setae;sternal and metasternal shields fused or separated.In male,such characteristics are as follows: shape and position of v1 and v2 on trochanter of palp;shape of gnathotectum,tritosternum,spermatodactyl,arthrodial brush,fixed and movable digits;tooth number on fixed and movable digits;the the shape and length of h1–h3 and pcx;genital lamina present or absent,av1 and av2 on femur ?,av1 genu ?,av1 tibia ?,and so on.In deutoymph,these characteristics are as follows: shape of sternal shield,dorsal shields,idiosoma setae,gnathotectum,v1 and v2 on palp trochanter,number of setae on dorsal shields and position of JV4.The common features at family level: These characteristics are common,without obvious variation,to subfamilies and genera and are not generally used for classification of lower taxa.In female,such characteristics are setal length on dorsum setae,palp length,shape of tritosternum and arthrodial brush.Such characteristics are,in male,locations of idiosomal setae,shape of genital pore,number and shape of glandular pores,and length of peritrematal groove.And in deutonymph,the characteristics are shape of peritrematal shield and ritosternum,length of peritrematal groove.In larvae and protonymphs,known from a few of species only,although the morphological variation of characteristics is not obvious,the applicability of their characteristics cannot be scientifically evaluated at present.2 Morphogenetic parttern in representive speciesThe observation on the ontogenetic morphology of four presentive species,Cornigamasus allotritosternus Yao et al.,2020,Parasitus yuensis Ma & Lin,2008,Phorytocarpais americanus Berlese,1888 n.comb and Rbdocarpais clavasetosus Ma,2012 n.comb.,showed that,in lifetime of Parasitidae individual,its idiosomal color gradually darkened,ossification gradually strengthened,setal number gradually increased and their shape gradually varied.The changes in idiosomal color,the number of setae and the length of peritrematal groove occurred mainly in deutonymph,and the changes in setal form and appearance of dorsal and ventral shields mainly emerged in adult mites.During the postembryonic development,ten pairs of setae on palp were added,of which five pairs were added in protonymph and deutonymph,respectively.51 pairs of setae on leg(excluding tarsus I)were added,including 5 pairs in protonymph and 46 pairs in deutonymph.The setae of the female and male on the palps and legs are same to the deutonymph in number and shape,while idiosomal setae are same to or different from deutonymph in number and shape.The homologies of subcapitular setae h1 and h2 and dorsal setae s4 and r3:according to the location,the morphological characteristic and the occurrence sequence of subcapitular setae,h2 in the larva is homologous to h3 in the adults,that is,the h3 in adults is actually same to h2 in larva.s4 in the larva is homologous to r3 in the adults,There are two cases: according to the system of idiosomal setal nomenclature by Lindquist & Evans(1965),r3 in the adults should be renamed s4;according to the common the system of idiosomal setal nomenclature in Parasitidea,s4 in the adults should be renamed r3.3 The taxa new to science and China and the redesigned taxaA total of more than 5000 parasitidae specimens from 22 provinces(municipalities and autonomous regions)in China were examined,and 69 species of 20 genera were identified.In the identified taxa,two genera and 40 species are new to science,two genera and six species are new to China.There were 141 species in 14 genera previously reported in China,of which one genus and four species were recognized as the misidentified taxa,and 57 species were changed their taxonomic status,as new combinations,according to the present taxonomic system of the family.Therefore,actual parasid taxa are 138 species and 20 genera previously known in China.And this study makes the Chinese parasid mites inceased to 182 species,24 genera and 2subfamilies.In this dissertation,the identified taxa are described detailly with a species catalog including the new combinations and the keys to subfamilies,genera and species.4 Phylogenetic relationships at generic levelThe phylogenetic relationship of Parasitidae is explored preliminarily with constructed strict consensual tree using TNT software based on codes of 67 morphological traits in females of the selected 102 species belonging to 40 genera in this study.The consensual tree indicates that the division of Parasitidae 2 subfamily is reasonable,but the classification status of Anadenosternum,Eugamasus,Neogamasus,Phytiogamasus,Schizosthetus,Sinogamasus,Thalassogamasus and Vulgarogamasus are different from the existing classification system,indicating that their phylogenetic relationships need to be furtherly verified and discussed;Bacuterus,Gamasodes,Cornigamasus,Cycetogamasus,Phorytocarpais,Poecilochirus,Rhabdocarpais and Trachygamasus are monophyletic groups;Anchigamasus and Anidogamasus,Aclerogamasus and Tanygamasus,Holoparasitus and Meriadenogamasus,Tomeogamasus and Pergamasus,Zelogamasus and Phytiogamasus are sister groups.By the comprehensive taxonomic study on Chinese Parasitidae,the characteristics and traits with taxonomic significance were valuated based on their variabilty in Parasitidae,the changes of main characteristics in morphogenesis of the representive species were presented,the misidentified genera and species were revised.The results greatly increased known parasitid species in China and provided a basis for further research on Parasitidae.